1. Field of the Invention
The present invention relates to separable electrical connectors and more particularly to improvements in manufacturing separable electrical connectors, such as loadbreak connectors and deadbreak connectors, wherein a sleeve of low coefficient of friction material is provided during a molding process to protect the critical electrical interfaces of the connector from contamination. The sleeve further provides for ease of connection and disconnection of the resulting molded connector.
2. Description of the Prior Art
Loadbreak connectors used in conjunction with 15 and 25 KV switchgear generally include a power cable elbow connector having one end adapted for receiving a power cable and another end adapted for receiving a loadbreak bushing insert. The end adapted for receiving the bushing insert generally includes an elbow cuff for providing an interference fit with a molded flange on the bushing insert. This interference fit between the elbow cuff and the bushing insert provides a moisture and dust seal therebetween. An indicator band may be provided on a portion of the loadbreak bushing insert so that an inspector can quickly visually determine proper assembly of the elbow cuff and the bushing insert.
The elbow cuff forms a cavity having a volume of air which is expelled upon insertion of the bushing insert. During initial movement of the loadbreak connectors in the disassembly operation, the volume of air in the elbow cavity increases but is sealed off at the elbow cuff resulting in a decrease in pressure within the cavity. The dielectric strength of the air in the cavity decreases with the decrease in air pressure. Although this is a transient condition, it occurs at a critical point in the disassembly operation and can result in dielectric breakdown of the opening interface causing a flashover or arc to ground. The occurrence of flashover is also related to other parameters such as ambient temperature, the time relationship between the physical separation of the connectors and the sinusoidal voltage through the loadbreak connectors.
Another reason for flashover while switching loadbreak connectors, prior to contact separation, is attributed to a decrease in dielectric strength of the air along the interface between the bushing insert and the power cable elbow to ground. As earlier described, a decrease in air pressure is momentarily formed by the sealed cavity between the elbow cuff and the bushing insert flange. The lower pressure in the cavity reduces the dielectric strength of the air along the connection interface possibly resulting in flashover.
One drawback with loadbreak connectors of the prior art is the difficulty involved in inserting one end of the loadbreak bushing insert into the power elbow connector and inserting the opposite end of the loadbreak bushing insert into a bushing well. In particular, because the interface surfaces of the loadbreak bushing insert and the power elbow connector and the bushing well are typically made from a rubber material, the frictional forces engaged in inserting the loadbreak bushing insert are substantial, even when lubricated. In other words, the rubber to rubber surfaces typically stick together upon assembly of the loadbreak connector.
Other drawbacks with these type of connectors relate to the problems encountered during manufacturing. Typically, these connectors are made by injection molding of a rubber or an epoxy material wherein the critical electrical interfaces are formed by molding the material against a metal mold surface. To prevent the material from sticking to the mold surface, release agents are typically sprayed in the mold cavities. Once cured, the connector is removed from the mold and, due to the nature of the molding material, a considerable amount of mold flashing must be trimmed. Even when trimmed properly, mold parting lines on the connector interface surfaces may disrupt the required connector seal and result in an electrical short. Also, the mold cavities are typically prone to contaminants, which may in turn be imparted onto the electrical interface of the connector resulting in a scrapped part.
Accordingly, it would be advantageous to provide a method for manufacturing a molded electrical connector which reduces or prevents the aforesaid manufacturing problems. It would also be desirable to provide a separable electrical connector system which is easily assembled and disassembled with a mating connector and is quickly visually inspected to determine proper assembly. It would further be advantageous to provide such a system with a visible identification of the operating voltage class of the connectors.